Electric incandescent lamp



ELECTRIC INCANDESCENT LAMP Filed May 5, 1927 VP vm o m m n fi m 0% c Em WWW" Patented May 21, 1929.

UNITED STATES PATENT OFFICE.

FRITZ ECKHABD'IKAND m HOHNEKAMP, OF EISENAOH, Gamay.

ELECTRIC INCAN-DESCENT mun.

Application filed May 5, 1927, Serial No. 189,140, and in Germany September 87, 1988.

This invention relates to electric incandescent lamps which are suitable to be used in series with one another and of the kind in which a shunt is permanently connected to the ends of the incandescent filament, which shunt is made of a material which is not conductive as long as the normal voltage of the lamp is applied to its ends and which becomes conductive as soon as a higher voltage is applied thereto.

An arrangement of this character which is considered to be in the nature of a safety device ensures that when several lamps are connected in series with one another to the supply circuit, the current flows only through the filaments of the lamps as long as the incandescent filaments are in good condition. However, when an incandescent filament is destroyed, the whole of the supply voltage is applied to the ends of the corresponding shunt, which becomes conductive so that the other lamps of the series continue to be incandescent. The shunt is preferably made so that when it has become conductive its resistance is substantially equal to the resistance of the incandescent filamentthat has been destroyed, so that the conditions of the other lamps, which continue to be incandes cent, remain substantially unaltered.

It has been found that the substances which have hitherto been used for such shunts do not possess the necessary constancy or they are diflicult to manipulate or to mount.

The present invention consists in making the said shunt of such chemical compounds of metals, as they are found in form of ores, viz, sulphides or oxides and mixtures thereof,

either in the natural form or in a calcined state or as a mixture thereof. These substances are used either in the form of solid pieces or in small particles, such as in the form of grains or powder, either alone or mixed with small particles of other conductive or non-conductive substances or with small particles of such substances mixed with one another.

Instead of ores or of substances obtained from ores by calcining, use may be made of other substances having the same chemical composition, which are produced by synthesis from the component parts.

When use is made of ores in the form of sulphides, we employ more particularly those having a metallic lustre or pyrites. Galena has been found to be especially useful. Of

the oxides, metallic iron oxide (Fe,O may be mentioned by way of example.

All the substances above referred to are especially suitable for carrying the invention into efiect because they are very insensitive to atmospheric influences and moisture. Further, they have a high limit, that is to say, the. voltage at which these substances suddenly pass from the non-conductive to the conductive state is rather high. For this reason, when substances of this character are employed, they do not require the same great care as the substances which have hitherto been used; more particularly they need not be arranged loosely in their containers but they can be firmly pressed in, which also contributes towards increasing the constancy of the shunts thus produced. It is entirely immaterial at which points these shunts are arranged between the ends of the filaments. They may be mounted in the holder or in the socket of the lamp, or even in the lamp itself. However, they are preferably mounted in the lower part of the lamp (in the lam foot) in such a manner that they connect irectly to leads in the lamp.

The invention also relates to another arrangement for increasing the reliability of lamps by means of shunts or safety devices, the conductivity of which is varied by an increase in the voltage and it consists in this that the lamp is provided with two incandescent filaments which are connected together by means of a shunt of the character above referred to in such a manner that upon one of the filaments being destroyed, the current will flow through the shunt and the second filament.

The two arrangements may be combined together in such a manner that upon the two filaments being destroyed, the other lamps which are connected in series therewith will continue to be incandescent.

With this object in view, a filament which has been provided with a shunt between the two ends of the filament is provided with a second incandescent filament which is connected at one end with one end of the first incandescent filament and at its other end with the other end of the first incandescent filament through a second shunt, which is also of such a character that it is not conductive for the normal voltage of the incandescent filament but becomes conductive as soon as the said valtage is increased. By suitably choosing the materials and dimensions of the second shunt, the voltage required for rendering the latter conductive can be made smaller than the voltage that is required for rendering conductive the shunt arranged across the ends of the first incandescent filament.

In an arrangement as j ust referred to, when the first filament is burnt through, first of all the second shunt becomes conductive so that the second incandescent filament is brought into the circuit whilst the first shunt is still non-conductive. However, when the second incandescent filament is destroyed, the whole of the voltage is applied for a moment to the first shunt and bridges over the ends of the incandescent filament, although the other lamps which are connected in series with this lam continue to be alight.

T e invention is illustrated b way of example in the accompanying rawings, in which Figure 1 shows the application of the invention to a lamp with one incandescent filament,

Figure 2 its use in connection with a lamp having two incandescent filaments, whilst Figure 3 is a simplified form of lamp provided with two incandescent filaments.

Referring to Figure 1, a is a bulb of the lamp, 6 the lower narrower part thereof, viz, the neck, a is the foot, into which the 1 leads (I of the incandescent filament i are fused.

The incandescent filament z is dimensioned for a voltage of 14 volts. The hollow part of the foot is closed up by a stopper 7 of suitable material, such as asbestos, and a layer of cement g. A layer e of grains of galena is placed in the hollow space which is left free etween the fused end of the foot 0 and the stopper 7 and through which the connecting wires k pass to the leads d, so that the said layer makes direct contact with the connecting wires k. In the construction shown in this figure, the whole space is not completely filled up with the layer e so that an air space It is left free; however, the layer may be arranged to completely fill the whole of the hollow space, moreespecially in the case of galena.

Z is a glass bottom, m a bottom contact, n a screwthreaded sleeve, these three parts constituting together the socket of the lamp.

The two connecting wires are connected to the bottom contact m and the screw-threaded sleeve respectively.

The 0 eration of the lamp hereinbefore described 15 as follows: WVhen the lamp is connected in series with other lamps to a source of current, the whole of the current will flow along the following path z-n, 7a,, a, is, m, whilst no current will pass through the shunt formed by the layer e of galena since the 14 volts will not be sufficient for this purpose. However, when the filament z is destroyed, the full voltage of the source of current (for instance, 110 volts) will first of all be applied to the two wires k and this voltage will be sufiicient to render the shunt conductive. When the galena has thus become conductive, it will acquire when properly dimensioned, for instance for the properly chosen distance between the two conducting wires in and 70,, a resistance which is approximately equal to the resistance of the filament when incandescent, so that a voltage of 14 volts will again be applied to the contacts m and n with the result that the voltage conditions for the other lamps are the same as before the filament i was destroyed.

In Figure 2, which illustrates a lamp without a socket, use has been made of the same references as have been mentioned with respect to Figure 1 for denoting similar parts. In this form of construction a second filament i is provided in addition to the filament 1:, which second filament is also dimensioned for a voltageof 14 volts, one end thereof being connected to the same lead as the one end of the filament 2'. However, the other end of the 1 filled with galena, the arrangement being such that the distance between 7:, and k is smaller than the distance between k and 1b,.

The operation of the lamp just referred to is as follows: When the lamp is connected in series with the other lamps to a source of current, for instance altogether seven lamps across a voltage of 110 volts, the current first of all flows along is, 2' 70,, because the "oltage of 14 volts between the wire In, and the wire k is not suilicient to render conductive the galena between it, and 7a or between k, and 70 However, when the filament i is destroyed, the whole of the voltage, viz, 110 volts, is m0- mentarily applied on the one hand between the wires 70 and 7c and on the other hand between the. wires lc, and k This voltage is sufiicient to render the galena conductive and since the distance between 70 and k is smaller than the distance between is; and it, the part between is, and is, will become conductive first, so that the filament i will nott be inserted into the circuit and the same con ditions will apply as before the destruction of the filament i so that a voltage of approximately 14 volts will again be applied between is and 70 which voltage is not sufficient to render the shunt between the wires 70 and la, c onductive. However, when also the filament i is destroyed, the whole of the voltage, viz, 110 volts, will again be applied momentarily to the wires is and 70 and, as in the first form of construction, the current will pass from k to is, through the galena, so that although this lamp is no longer in operation, the other lamp will continue to remain incandescent.

The lamp illustrated in Figure 3 is similar to the lamp illustrated in Figure 2, the di flerence being that the connecting wire is surrounded by an insulation p where it passes through thelayer of galena e. As long as the current passes through the filament i, a voltage of about 14 volts will be applied to is, and 10 so that no current will pass through the galena 6 between these two filaments. However, when the filament z' is destroyed the voltage of the supply circuit will be applied to k, and 70 and the mass of galena between the two filaments will become conductive and the current will flow from 7a through the filament i and 70 and the mass of galena e to 7:1

What we claim is 1. An electric incandescent lamp having an incandescentfilament and a shunt permanently connected to the ends of the said filament and consisting of a sulphide ore, said shunt being non-conductive when the normal voltage of the lamp is applied thereto, but becoming conductive when a higher voltage is applied to it.

2. An electric incandescent lamp having an incandescent filament and a shunt permanently connected to the ends of the said filament and consisting of galena, said shunt being non-conductive when the normal voltage of the lamp is applied thereto but becoming conductive when a higher voltage is apphed to it.

3. An electric incandescent lamp having two leading contacts, a filament across the said two contacts, a second incandescent filament connected at one end to one of the said leading contacts and a shunt permanently connected between thesecond end of the sec- 0nd incandescent filament and the second leading contact, the said shunt consisting of ore and being non-conductive when the normal voltage of the lamp is applied thereto but becoming conductive when a higher voltage is applied to it.

age is applied to it, and a second shunt which is permanently connected between the ends of the first incandescent filament and is made of such a material and is so dimensioned that it is not conductive when the normal voltage of the lamp is applied thereto but becomes conductive when a voltage is applied to it which is higher than the voltage that renders the first shunt conductive.

5. An electric incandescent lamp having an incandescent filament and a shunt connected to said filament, said shunt consistin of an ore and being non-conductive when the normal voltage of the lamp is applied thereto but becoming conductive when a bi her voltage is applied to it and having 5 cient resistance on becoming conductive to prevent the shunt from functioning substantially as a dead short circuit.

6. An electric incandescent lamp having an incandescent filament and a shunt connected to said filament, said shunt consisting of a compound and be non-conductive when the normal voltage 0 the lamp is applied thereto but becomin 'conductive when a higher voltage is applie to it and having sufficient resistance on becoming conductive to prevent the shunt from functioning substantially as a dead short circuit.

In testimony whereof we have signed our names to this specification.

FRITZ ECKHABDT. MAXHOHNEKAMP, 

